Preparation of polymer having isoindole structures

ABSTRACT

A polymer having an isoindole structure represented by the following general formula: ##STR1## 
     wherein R 1 , R 2  and R 3  independently represent a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms, X -  represents an anion of an electrolyte, y is a number of from 0.01 to 1, which indicates the proportion of the anion to 1 mole of the monomer, and n is a number of from 5 to 500, which indicates the degree of polymerization, 
     shows a high electroconductivity when doped, and the stability of the polymer in the oxidized state is high. This polymer is obtained by subjecting an isoindole compound represented by the following general formula: ##STR2## wherein R 1 , R 2  and R 3  are as defined above, to (1) electrochemical polymerization in the presence of an electrolyte in a solvent or (2) oxidative polymerization in a solvent by the action of an oxidant.

This is a division of application Ser. No. 092,916 filed Aug. 6, 1987,now U.S. Pat. No. 4,833,231.

TECHNICAL FIELD

The present invention relates to a novel electroconductive polymerhaving an isoindole structure, which is very stable and shows a veryhigh electroconductivity when doped, and a process for the preparationthereof.

This polymer can be used for the production of an electrode, anelectrochromic display element, a solar cell, an electric connection, adevice for the absorption and conversion of electromagnetic waves, and areversible oxidation-reduction system in the fields of electric andelectronic industries.

BACKGROUND ART

Recently, rapid progress has been made in reducing the weight,decreasing the thickness, and reducing the size of electric andelectronic instruments, and there is a strong demand for a reduction ofthe weight, a decrease in thickness, and a reduction in size of variouselectromagnetic material elements used for these instruments. In thisconnection, a development of novel materials having further improvedproperties is also strongly demanded.

New electroconductive materials have been widely developed to satisfythese demands. For example, since polyacetylene is given anelectroconductivity as high as 10² to 10³ s/cm by doping with iodine orarsenic pentafluoride [see Synthetic Metals, Volume 1, No. 2, page 101(1979/1980)] and has excellent charge-discharge characteristics,polyacetylene has been investigated as an electrode material of asecondary battery. Moreover, since polyacetylene has absorptioncharacteristics such that beams to be absorbed are close to solar beams,polyacetylene is under examination as a material of a solar cell.

However, polyacetylene is easily oxidized and doped polyacetylene isvery sensitive to moisture. Moreover, arsenic pentafluoride or the likeused for manifesting a high electroconductivity is highly toxic and isdangerous to the human body.

Polythiophene is under examination as an electroconductive material orbattery electrode material because it has a conjugated structure similarto that of cis-type polyacetylene, and a peculiar electron structurecontaining sulfur atoms. Moreover, polythiophene is under investigationas an electrochromic material in which the color is changed by doping.For example, A. M. Druy et al reports that if 2,2'-bithienyl iselectrochemically polymerized, a color change of blue-red is caused inthe formed polymer in the oxidized state-reduced state and this changeis reversible, and the polymer is valuable as an electrochromic material[J. de. Physique, 44, 6, C3-595 (1983)].

However, polythiophene has a problem in that since polythiophene isunstable in the doped state and is easily dedoped, it is difficult tomaintain a high electroconductivity.

In view of the foregoing defects of the conventional techniques, it is aprimary object of the present invention to provide a novel polymer whichis very stable in air and can be easily doped with an ordinary dopant sothat it is possible to maintain a high electroconductivity.

DISCLOSURE OF THE INVENTION

The polymer according to the present invention is a polymer having anisoindole structure represented by the following general formula:##STR3## wherein R¹, R² and R³ independently represent a hydrogen atomor a hydrocarbon group having 1 to 5 carbon atoms, X⁻ represents ananion of an electrolyte, y is a number of from 0.01 to 1, whichindicates the proportion of the anion to 1 mole of the monomer, and n isa number of from 5 to 500, which indicates the degree of polymerization.

The polymer of the present invention can be easily prepared according tovarious polymerization processes.

According to a typical process, an isoindoline compound represented bythe following general formula (IIa): ##STR4## wherein R¹, R² and R³ areas defined above, or an isoindole compound represented by the followinggeneral formula (IIb): ##STR5## wherein R¹, R² and R³ are as definedabove, is subjected to (1) electrochemical polymerization in thepresence of an electrolyte in a solvent or (2) oxidative polymerizationin a solvent by the action of an oxidant.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an infrared absorption spectrum diagram of the polyisoindoleprepared in Example 1-1;

FIG. 2 is an infrared absorption spectrum diagram of the polyisoindoleprepared in Example 2;

FIG. 3 is an infrared absorption spectrum diagram of thepoly(2-methylisoindole) prepared in Example 6-1;

FIG. 4 is an infrared absorption spectrum diagram of thepoly(2-methylisoindole) prepared in Example 7;

FIG. 5 is a diagram showing the change of the visible spectrum ofpolyisoindole at the steps of doping and dedoping, which was obtained bythe electrochromic material test described in Reference Example (a);

FIG. 6 is a diagram showing the change of the visible spectrum ofpoly(2-methylisoindole) at the steps of doping and dedoping, which wasobtained by the electrochromic material test described in ReferenceExample (b);

BEST MODE FOR CARRYING OUT THE INVENTION

The polymer having an isoindole structure in the neutral state (i.e.,the dedoped state) is represented by the general formula (Ia), and thepolymer having an isoindole structure in the doped state is representedby the general formula (Ib). These polymers are reversible.

As the polymer having the isoindole structure represented by the generalformula (Ia), there can be mentioned polyisoindole,poly(2-methylisoindole), poly(2-ethylisoindole),poly(2-phenylisoindole), poly(5-methylisoindole),poly(5-ethylisoindole), and poly(5,6-dimethylisoindole). As the anion X⁻of the polymer having the isoindole structure represented by the generalformula (Ib), there can be mentioned Cl⁻, Br⁻, I⁻, ClO₄ ⁻, BF₄ ⁻, PF₆ ⁻,AsF₆ ⁻, SbF₆ ⁻, AlCl₄ ⁻, AlBr₃ Cl⁻, FeCl₄ ⁻, SnCl₃ ⁻ and CF₃ SO₃ ⁻.

The polymer having an isoindole structure according to the presentinvention is characterized in that (i) a very high electroconductivityis manifested by doping, (ii) oxidation-reduction can beelectrochemically performed repeatedly and an inherent color is shown ineach state, and (iii) the polymer is stable in the oxidized state.

The polymer of the present invention can be obtained by polymerizing anisoinsoline compound represented by the general formula (IIa) or anisoindole compound represented by the general formula (IIb).

As the isoindoline compound represented by the general formula (IIa),there can be mentioned, for example, isoindoline, 2-methylisoindoline,2-ethylisoindoline, 2-phenylisoindoline, 5-methylisoindoline,5-ethylisoindoline, and 5,6-dimethylisoindoline.

As the isoindole compound represented by the general formula (IIb),there an be mentioned, for example, isoindole, 2-methylisoindole,2-ethylisoindole, 2-phenylisoindole, 5-methylisoindole,5-ethylisoindole, and 5,6-dimethylisoindole.

An appropriate solvent is selected according to the kind of thepolymerization process as the solvent to be used for polymerization ofthe above-mentioned isoindoline compound or isoindole compound, and thekind of the solvent is not particularly critical. Generally speaking,where the isoindoline compound represented by the general formula (IIa)or the isoindole compound represented by the general formula (IIb) iselectro-chemically polymerized in the presence of an electrolyte, therecan be used, for example, acetonitrile, benzonitrile, propionitrile,dioxane, tetrahydrofuran, sulfolane, propylene carbonate, and tertiarybutyl alcohol.

Where the isoindoline compound represented by the general formula (IIa)or the isoindole compound represented by the general formula (IIb) isoxidatively polymerized, there can be used, for example,dichloronethane, chloroform, carbon tetrachloride, dichloroethane,tetrachloroethane, nitromethane, nitroethane, nitrobenzene,chlorobenzene, N-methyl-2-pyrrolidone, and carbon disulfide.

As the electrolyte used in the electrochemical polymerization process,there can be mentioned tetraethylammonium bromide, tetraethylammoniumchloride, tetra-n-butylammonium bromide, tetra-n-butylammonium chloride,tetraphenylphosphonium bromide, and tetraphenylphosphonium chloride.

As the oxidant used in the oxidative polymerization process, there canbe used quinones such as 2,3-dichloro-5,6-dicyano-1,4-benzoquinone,tetrachloro-1,2-benzoquinone, and tetrachloro-1,4-benzoquinone, andhalogens such as iodine and bromine.

The polymerization temperature adopted for polymerization of theabove-mentioned isoindoline compound or isoindole compound is determinedaccording to the polymerization process and is not particularlycritical. In general, however, preferably the polymerization is carriedout at a temperature in the range of from -80° C. to +200° C. Thepolymerization time is changed according to the polymerization process,the polymerization temperature and the structure of the isoindolinecompound or isoindole compound and is not simply defined, but generallypreferably, the polymerization is conducted for 0.25 to 200 hours.

The isoindoline compound represented by the general formula (IIa) can besynthesized by known processes. For example, isoindoline in which all ofR¹, R², and R³ in the general formula (IIa) represent a hydrogen atomcan be proposed according to the process reported by J. Bornstein et alin J. Org. Chem. 22, 1255 (1957).

The isoindole compound represented by the general formula (IIb) can besynthesized by known processes. For example, isoindole in which all ofR¹, R², and R³ in the general formula (IIb) represent a hydrogen atom isproposed by R. Bonett et al in J. Chem. Soc. Perkin Tans. I, 1973, 1432,by J. Bornstein et al in J. Chem. Soc. Chem. Commun., 1972, 1149, by J.Bornstein et al in Tetrahedron, 35, 1055 (1979), and by G. M. Priestleyet al in Tetrahedron Lett., 1972, 4295. R. Bonett et al teach that ifisoindole is cation-polymerized in an acidic solvent, a polymer having adihydroisoindole structure as the recurring unit is formed. Furthermore,a substituted isoindole in which R¹ and R² in the general formula (IIb)represent a hydrocarbon group can be synthesized, for example, by theprocess proposed by R. Kreher et al in Heterocycles, 11, 409 (1978).

The so-obtained polymer having an isoindole structure according to thepresent invention is easily doped with an ordinary dopant and the dopedpolymer has an electroconductivity higher than 10⁻⁴ s/cm. Furthermore,oxidation and reduction can be electrochemically conducted repeatedly,and an inherent color manifested in each state. The polymer having anindole structure according to the present invention is characterized inthat it is stable in the oxidized state.

The present invention will now be described in detail with reference tothe following examples that by no means limit the technical scope of theinvention.

Note, in the examples, the ¹ H-NMR spectrum was measured by using TMS asthe internal standard and a spectrometer, Model R-24B, supplied byHitachi Ltd.

The infrared absorption spectrum was measured by using an infraredspectrophotometer, Model 270-50, supplied by Hitachi Ltd., and aninfrared spectrophotometer, Model 60SXFT, supplied by Nicolet. Theultraviolet and visible spectra were measured by an auto-recordingspectrophotometer, Model U-3400, supplied by Hitachi Ltd.

The electroconductivity was measured according to the four-terminalmethod.

The change of the visible spectrum of the polymer at the time ofdoping/dedoping was measured by a high-speed spectrometer, ModelFSM-201, supplied by Opelex, and an instantaneous multiple photometricsystem, Model MCDP-100, supplied by Union Giken.

The gel permeation chromatography was carried out by using a high-speedliquid chromatograph, Model 665, supplied by Hitachi Ltd., and a column,Showdex GPCA-802 or GPCA-804, supplied by Showa Denko K.K., inchloroform as the solvent, at a temperature of 25° C. and a flow rate of1.02 ml/min.

EXAMPLE 1 Preparation of polyisoindole by electrochemical polymerizationof isoindoline

An electrolyte shown in Table 1 and isoindoline obtained according tothe process of Bornstein et al were dissolved in a solvent which hadbeen subjected to the oxygen-removing treatment, and by using a platinumplate as the counter electrode, an ITO glass (indium tin oxide glass) asthe operating electrode, and Ag/Ag⁺ as the reference electrode, avoltage of 0.60 V based on the Ag/Ag⁺ electrode was imposed on theso-formed electrolytic solution in a nitrogen atmosphere. A dark greenfilmy product was precipitated on the ITO glass electrode. After apredetermined quantity of electricity had been applied, the ITO glasselectrode was taken out and washed with acetonitrile. Then, a voltage of-0.80 V based on the Ag/Ag⁺ electrode was imposed on an acetonitrilesolution containing 0.1 mole/1 of lithium perchlorate, which had beensubjected to the oxygen-removing treatment, to remove the anion doped atthe electrochemical polymerization. The ITO electrode was again washedwith acetonitrile and vacuum-dried.

To so-obtained polymers are shown in Table 1. The infrared absorptionspectrum of the yellowish brown polymer obtained in Example 1-1 was asshown in FIG. 1. The elementary analysis values were 82.54% for C.,4.51% for H, and 11.99% for N. Furthermore, from the results of the gelpermeation chromatographical analysis in chloroform, it was found thatthe molecular weight of the polymer was 2,300 as calculated aspolystyrene.

                                      TABLE 1                                     __________________________________________________________________________    Electrochemical Polymerization of Isoindoline                                                                 Properties of polymer                                                   Quantity     Electroconductivity                                              of applied                                                                          Electro-                                                                             after doping with                      Example                                                                            Isoindoline                                                                          Electrolyte                                                                          Solvent                                                                              electricity                                                                         conductivity                                                                         isodine                                No.  (millimole/1)                                                                        (millimole/1)                                                                        (ml)   (coulomb)                                                                           (σ.sub.RT) [s/cm]                                                              (σ.sub.RT)                       __________________________________________________________________________                                           [s/cm]                                 1-1  100    n-Bu.sub.4 NBr 200                                                                   CH.sub.3 CN 25                                                                       10    4 × 10.sup.-5                                                                  1 × 10.sup.-3                    1-2  100    n-Bu.sub.4 NBr 100                                                                   CH.sub.3 CN 20                                                                        3    --     --                                                        (CH.sub.3).sub.2 CO 5                                      1-3  100    n-Bu.sub.4 NCl 200                                                                   (CH.sub.3).sub.3 COH                                                                 10    --     --                                                        25                                                         1-4  100    n-Bu.sub.4 NCl 100                                                                   CH.sub.3 CN 24                                                                       10    2 × 10.sup.-5                                                                  --                                                        NMP 1                                                      1-5  200    Ph.sub.4 PCl 200                                                                     CH.sub.3 CN 25                                                                        5    --     --                                     1-6  200    Ph.sub.4 PCl 100                                                                     CH.sub.3 CN 20                                                                       10    3 × 10.sup.-5                                              PhCN 5                                                     1-7  200    Ph.sub.4 PBr 200                                                                     CH.sub.3 CN 25                                                                        7    --     --                                     1-8  200    Ph.sub.4 PBr 100                                                                     CH.sub.3 CN 20                                                                        3    --     --                                                        THF 5                                                      __________________________________________________________________________     Note                                                                          nBu.sub.4 NBr: tetran-butylammonium bromide                                   nBu.sub.4 NCl: tetran-butylammonium chloride                                  Ph.sub.4 PCl: tetraphenylphosphonium chloride                                 Ph.sub.4 PBr: tetraphenylphosphonium bromide                                  CH.sub.3 CN: acetonitrile                                                     PhCN: benzonitrile                                                            (CH.sub.3).sub.2 CO: acetone                                                  NMP: Nmethyl-2-pyrrolidone                                                    (CH.sub.3).sub.3 COH: tertiarybutanol                                         THF: tetrahydrofuran                                                     

EXAMPLE 2 Chemical preparation of polyisoindole by oxidativepolymerization of isoindoline

In 80 ml of dehydrated and oxygen-removed acetonitrile were dissolved2.38 g (0.020 mole) of isoindoline obtained in Example 1 and 12.3 g(0.050 mole) of chloranil, and reaction was carried out at 50° C. in anitrogen atmosphere for 5 hours. The precipitate was recovered byfiltration and was washed with methanol to obtain 1.3 g of a blackpolymer. The infrared absorption spectrum of the polymer was as shown inFIG. 2, and the spectrum was in agreement with the spectrum of thepolymer obtained in Example 1-1. The electroconductivity was 3×10⁻⁵s/cm.

EXAMPLE 3 Preparation of polyisoindole by electrochemical polymerizationof isoindole

An electrolyte shown in Table 2 and isoindole formed by thermallydecomposing 2-methoxycarbonyloxyisoindoline according to the process ofBonett et al were immediately dissolved in a solvent which had beensubjected to the oxygen-removing treatment in nitrogen to form anelectrolytic solution. By using a platinum plate as the counterelectrode, an ITO glass as the operating electrode, and Ag/Ag⁺ as thereference electrode, a voltage of 0.40 V based on the Ag/Ag⁺ referenceelectrode was imposed on the so-formed electrolytic solution at 0° C. ina nitrogen atmosphere. A dark green filmy product was precipitated onthe ITO glass electrode. After application of a predetermined quantityof electricity, the ITO glass electrode was taken out and washed withacetonitrile. A voltage of -80.0 V based on the Ag/Ag⁺ electrode wasimposed on an acetonitrile solution containing 0.1 mole/1 of lithiumperchlorate, which had been subjected to the oxygen-removing treatment,to remove the anion doped at the electrochemical polymerization. The ITOglass electrode was again washed with acetonitrile and vacuum-dried.

The infrared absorption spectrum of the so-obtained polymer was inagreement with that shown in FIG. 1.

                                      TABLE 2                                     __________________________________________________________________________    Electrochemical Polymerization of Isoindole                                                                   Properties of polymer                                                   Quantity     Electroconductivity                                              of applied                                                                          Electro-                                                                             after doping with                      Example                                                                            Isoindole                                                                            Electrolyte                                                                          Solvent                                                                              electricity                                                                         conductivity                                                                         isodine                                No.  (millimole/1)                                                                        (millimole/1)                                                                        (ml)   (coulomb)                                                                           (σ.sub.RT) [s/cm]                                                              (σ.sub.RT)                       __________________________________________________________________________                                           [s/cm]                                 3-1  100    n-Bu.sub.4 NBr 200                                                                   CH.sub.3 CN 25                                                                       10    2 × 10.sup.-5                                                                  3 × 10.sup.-3                    3-2  100    n-Bu.sub.4 NBr 100                                                                   CH.sub.3 CN 20                                                                       0.60  --     --                                                        (CH.sub.3).sub.2 CO 5                                      3-3  100    n-Bu.sub.4 NCl 200                                                                   CH.sub.3 CN 25                                                                       10    --     --                                     3-4  100    n-Bu.sub.4 NCl 100                                                                   CH.sub.3 CN 24                                                                       10    5 × 10.sup.-5                                                                  --                                                        PC 1                                                       3-5  200    Ph.sub.4 PCl 200                                                                     CH.sub.3 CN 25                                                                       5     --     --                                     3-6  200    Ph.sub.4 PCl 100                                                                     CH.sub.3 CN 20                                                                       10    7 × 10.sup.-5                                                                  --                                                        PhCN 5                                                     3-7  200    Ph.sub. 4 PBr 200                                                                    CH.sub.3 CN 25                                                                       3     --     --                                     3-8  200    Ph.sub.4 PBr 100                                                                     CH.sub.3 CN 20                                                                       3     --     --                                                        THF 5                                                      __________________________________________________________________________     Note                                                                          nBu.sub.4 NBr: tetran-butylammonium bromide                                   nBu.sub.4 NCl: tetran-butylammonium chloride                                  Ph.sub.4 PCl: tetraphenylphosphonium chloride                                 Ph.sub.4 PBr: tetraphenylphosphonium bromide                                  CH.sub.3 CN: acetonitrile                                                     PhCN: benzonitrile                                                            (CH.sub.3).sub.2 CO: acetone                                                  PC: propylene carbonate                                                       THF: tetrahydrofuran                                                     

EXAMPLE 4 Synthesis of polyisoindole by oxidative polymerization ofisoindole

To acetonitrile, which had been subjected to the dehydrating andoxygen-removing treatment and cooled to 0° C., were added 0.59 g (5millimoles) of isoindole and 1.48 g (6 millimoles) oftetrachloro-1,4-benzoquinone, and the mixture was stirred in a nitrogenatmosphere and the temperature was gradually elevated. Reaction wascarried out at 50° C. for 5 hours. The obtained precipitate wasrecovered by filtration and was washed with methanol to obtain 0.38 g ofa black polymer. The infrared absorption spectrum of this polymer was infull agreement with the spectrum of the polymer of Example 1 shown inFIG. 1, and the electroconductivity of the polymer was 2×10⁻² s/cm.

EXAMPLE 5

The procedures of Example 4 were repeated in the same manner except that2,3-dichloro-5,6-dicyano-1,4-benzoquinone was used instead oftetrachloro-1,4-benzoquinone and chloroform was used as the solvent, and0.35 g of a black copolymer was obtained. The infrared absorptionspectrum of this polymer was in full agreement with the spectrum shownin FIG. 4, and the electroconductivity of the polymer was 3×10⁻⁵ s/cm.

EXAMPLE 6 (a) Synthesis of 2-methylindole [R¹ =R² =H and R³ =CH₃ ingeneral formula (IIb)]

A 2-liter 4-neck flask equipped with a dropping funnel, a stirrer, athermometer, and a nitrogen-introducing inlet was charged with 15.0 g(0.057 mole) of o-xylylene dibromide, and this o-xylylene dibromide wasdissolved in 150 ml of oxygen-removed anhydrous diethyl ether. Then,10.5 g (0.23 mole) of methylhydrazine was dropped into the solution withstirring at 20° C. over a period of 30 minutes, and the mixture wasstirred at room temperature for 12 hours. The formed white precipitatewas recovered by filtration and a 20% aqueous solution of caustic soda,which had been subjected to the oxygen-removing treatment, was added tothe recovered solid. The mixture was then stirred for 3 hours in anitrogen atmosphere. Then, the formed suspension was extracted with 150ml of chloroform and the chloroform solution was washed twice with 100ml of water, and the chloroform solution was dried with potassiumcarbonate and concentrated under a reduced pressure. The formed yellowsolid was placed in a sublimation device and heated on an oil bath undera reduced pressure, and 2.6 g (0.020 mole) of 2-methylisoindole in theform of a white needle crystal was obtained at 85° C./10 mmHg in thebottom of a cooling zone of the sublimation device. When the nuclearmagnetic resonance spectrum (¹ H-NMR) of the obtained product wasdetermined in deuterated chloroform by using TMS as the internalstandard, the following results were obtained:

δ3.90 (s, 3H), 6.9 (m, 2H), 7.0 (s, 2H), 7.5 (m, 2H)

(b) Preparation of poly(2-methylisoindole) by electrochemicalpolymerization of 2-methylisoindole

An electrolyte shown in Table 3 and 2-methylisoindole were dissolved ina solvent at predetermined concentrations and the solution was bubbledby dry nitrogen for more than 30 minutes to remove oxygen and form anelectrolytic solution. In this electrolytic solution, electrochemicalpolymerization was carried out at room temperature with a predeterminedquantity of applied electricity under a constant voltage of 2.0 V byusing an ITO glass (indium tin oxide glass) having a surface resistanceof 20 Ω/□ as the sample electrode and a platinum plate as the counterelectrode. A yellowish brown film of poly(2-methylisoindole) was formedon the ITO glass sheet as the positive electrode.

A constant voltage of -1.5 V was imposed onto the formed film in anoxygen-removed acetonitrile solution containing 2 moles/1 of lithiumperchlorate by using a platinum plate as the counter electrode to removethe bromine ion doped at the electrochemical polymerization. Then, thefilm was again washed with acetonitrile and vacuum-dried.

The so-obtained polymers are shown in Table 3. The infrared absorptionspectrum of the yellowish brown polymer of Example 6-1 was as shown inFIG. 3. The elementary analysis values of the polymer were 83.71% for C,5.21% for H, and 11.03% for N. From the results of the gel permeationchromatographical analysis, it was found that the molecular weight was1700 as calculated as polystyrene. The above-mentioned found elementaryanalysis values were in full agreement with the calculated values(83.62% for C., 5.54% for H, and 10.84% for N) based on the followingstructure estimated from the foregoing results: ##STR6##

The nuclear magnetic resonance spectrum (¹ H-NMR) of the polymer wasdetermined in deuterated chloroform by using TMS as the internalstandard. The following results were obtained.

δ3.77 (s, 3H), 7.40 (m, 4H)

                                      TABLE 3                                     __________________________________________________________________________    Electrochemical Polymerization of 2-Methylisoindole                                                            Properties of polymer                                                   Quantity     Electroconductivity                                              of applied                                                                          Electro-                                                                             after doping with                     Example                                                                            2-Methylisoindole                                                                      Electrolyte                                                                          Solvent                                                                             electricity                                                                         conductivity                                                                         isodine                               No.  (millimole/1)                                                                          (millimole/1)                                                                        (ml)  (coulomb)                                                                           (σ.sub.RT) [s/cm]                                                              (σ.sub.RT)                      __________________________________________________________________________                                            [s/cm]                                6-1  78.0     n-Bu.sub.4 NBr 200                                                                   CH.sub.3 CN 25                                                                      10    8 × 10.sup.-6                                                                  3 × 10.sup.-4                   6-2  78.0     n-Bu.sub.4 NBr 200                                                                   CH.sub.3 CN 20                                                                      0.60  --     --                                                         CH.sub.2 Cl.sub.2 5                                      6-3  78.0     n-Bu.sub.4 NCl 200                                                                   CH.sub.3 CN 25                                                                      10    --     --                                    6-4  78.0     n-Bu.sub.4 NCl 200                                                                   CH.sub.3 CN 24                                                                      10    5 × 10.sup.-6                                                                  --                                                         NMP 1                                                    6-5  100      Ph.sub.4 PCl 200                                                                     CH.sub.3 CN 25                                                                      10    --     --                                    6-6  100      Ph.sub.4 PCl 200                                                                     CH.sub.3 CN 20                                                                      10    6 × 10.sup.-6                                               PhCN 5                                                   6-7  100      Ph.sub.4 PBr 200                                                                     CH.sub.3 CN 25                                                                      10    --     --                                    6-8  100      Ph.sub.4 PBr 200                                                                     CH.sub.3 CN 20                                                                      10    --     --                                                         PhCN 5                                                   __________________________________________________________________________     Note                                                                          nBu.sub.4 NBr: tetran-butylammonium bromide                                   nBu.sub.4 NCl: tetran-butylammonium chloride                                  Ph.sub.4 PCl: tetraphenylphosphonium chloride                                 Ph.sub.4 PBr: tetraphenylphosphonium bromide                                  CH.sub.3 CN: acetonitrile                                                     PhCN: benzonitrile                                                            CH.sub.2 Cl.sub.2 : dichloromethane                                           NMP: Nmethyl-2-pyrrolidone                                               

EXAMPLE 7 Chemical preparation of poly(2-methylisoindole) by oxidativepolymerization of 2-methylisoindole

2-Methylisoindole was synthesized according to the process disclosed inExample 6-(a). In 80 ml of dehydrated chlorobenzene were dissolved 2.0 g(0.15 mole) of 2-methylisoindole and 10.4 g (0.458 mole) of2,3-dichloro-5,6-dicyano-1,4-benzoquinone, and reaction was carried outunder boiling in a nitrogen atmosphere for hours. The formed precipitatewas recovered by filtration and washed with hot methanol to obtain 1.6 gof a black polymer. The infrared absorption spectrum of the obtainedpolymer was as shown in FIG. 4. The electroconductivity of the polymerwas 5.0×10⁻⁷ s/cm.

REFERENTIAL EXAMPLE

This example illustrates that the isoindole polymer obtained accordingto the present invention is valuable as an electrochromic displaymaterial.

(a) An electrode covered with polyisoindole obtained in Example 1-2 anda platinum mesh electrode were immersed in an acetonitrile solutioncontaining 1.0 mole/l of lithium perchlorate. When the voltage betweenthe electrodes was changed in the range of from -60.0 V to +3.0 V, itwas found that the color of the polyisoindole was reversibly changedfrom yellowish brown to green. This change of the color is shown as thevisible spectrum in FIG. 5. In FIG. 5, curve 1 indicates the spectrum inthe neutral state. An increase of the curve number indicates the advanceof doping. The color was changed to green from yellowish brown with thisadvance of doping.

(b) An electrode covered with poly(2-methylisoindole) obtained inExample 6-2 and a platinum mesh electrode was immersed in a solution oftetra-n-butylammonium tetrafluoroborate in water/acetonitrile (9/1volume ratio) and the voltage between the electrodes was changed in therange of from -1.5 V to +2.5 V. It was found that the color ofpoly(2-methylisoindole) was reversibly changed from yellowish brown toblue. This change of the color is shown as the visible spectrum in FIG.6. In FIG. 6, curve 1 shows the spectrum in the neutral state, and anincrease of the curve number indicates an advance of doping. The colorwas changed from yellowish brown to blue with the advance of dopant.

CAPABILITY OF EXPLOITATION IN INDUSTRY

The polymer having an isoindole structure according to the presentinvention is valuable as an electrode, an electrochromic displayelement, a solar cell, an electric connection, a device for absorbingand converting electromagnetic waves, and a reversibleoxidation-reduction system in the fields of the electric and electronicindustries.

What is claimed is:
 1. A process for the preparation of a polymer havingan isoindole structure containing monomer units selected from the groupconsisting of monomer units of the formula: ##STR7## wherein R¹, R² andR³ independently represent a hydrogen atom or a hydrocarbon group having1 to 5 carbon atoms, X⁻ represents an anion of an electrolyte, y is anumber of from 0.01 to 1, which indicates the proportion of the anion to1 mole of the monomer, and n is a number of from 5 to 500, whichindicates the degree of polymerization,which comprises subjecting anisoindoline compound represented by the following general formula (IIa):##STR8## wherein R¹, R² and R³ are as defined above, or an isoindolecompound represented by the following general formula (IIb): ##STR9##wherein R¹, R² and R³ are as defined above, to oxidative polymerizationin a solvent by the action of an oxidant.